The present invention relates, in general, to door systems for transit vehicles and, more particularly, the instant invention relates to door systems for ground level and platform boarding.
Transit vehicles are required which provide for passenger boarding and discharging from either an elevated platform or from ground level. Such a vehicle has a stairway leading downward from the floor of the vehicle to an elevation close to the ground, so that passengers are enabled to board from ground level, or to exit to ground level. The vehicle also has a moveable trap door which may be placed in a deployed position in which it covers the stairway and acts as a bridge permitting passengers to exit to a platform.
A prior art door system for such a vehicle is described in U.S. Pat. No. 5,070,794. That patent describes a vehicle having a door with an upper section and a lower section. It has a trap door which is pivotally mounted beside the stairway and is rotated downward to cover the stairway for platform boarding. In that patent, the trap door is referred to as a stairwell platform. In the case of platform boarding, only the upper section of the door is opened. The lower section of the door remains in its closed position. The lower section of the door has a threshold along its upper edge, the threshold bridging a gap between the trap door and the platform. The floor of the transit vehicle, the trap door, the threshold and the platform are all at substantially the same level.
For loading and discharging passengers at ground level, the trap door is rotated upward so that the stairway is uncovered. Then, when the door is opened, the lower section of the door moves with the upper section so that the lower section does not prevent passengers from exiting and entering the transit vehicle.
This type of door requires slide rails for both the upper and lower sections of the door. It also requires a lock to connect the lower section to the upper section so the lower section moves with the upper section during ground level boarding.
The present invention is a door system for a transit vehicle having a vehicle body with a full height door opening, which is for alternatively boarding from ground level and boarding from a platform. The transit vehicle has a floor, a stairway for ground level boarding and a trap door positionable in a deployed position for covering the stairway for platform boarding. The trap door is also positionable in a stowed position not covering the stairway for ground level boarding. The door system has a full height sliding door for covering and uncovering the door opening and a threshold which is disposed within the sliding door when the sliding door is closed. The threshold is positioned at substantially the elevation of the floor. A retention mechanism is attached to the threshold, the retention mechanism is activated when the trap door is in the deployed position to engage the trap door and release the sliding door so that when the sliding door is opened, the threshold is retained to fill a gap between the trap door and the platform. When the trap door is in the stowed position, the retention mechanism disengages the trap door and engages the sliding door so that the threshold moves with the sliding door and does not interfere with street level street level boarding.
It is therefore one of the primary objects of the present invention to provide a door system for a transit vehicle which provides, alternatively, for boarding from a platform or from ground level.
It is a further object of the present invention to provide a transit vehicle door system for, alternatively, platform boarding or ground level boarding in which the door system has a single full height door which is moved between an open position and a closed position.
Still another object of the present invention is to provide a transit vehicle door system for, alternatively, platform boarding or ground level boarding in which the door system includes a single full height door which is moved between an open position and a closed position and wherein the system has a threshold for covering a gap between a trap door and a platform during platform boarding.
Yet another object of the present invention is to provide a transit vehicle door system for platform boarding or ground level boarding which does not require two independently moving door panels.
A further object of the present invention is to provide a transit vehicle door system for platform boarding or ground level boarding which does not require support rails for independently moving door panels.
An additional object of the present invention is to provide a transit vehicle door system for platform boarding or ground level boarding having a full height door with a threshold disposed within the door in which the threshold is retained so it stays in position and does not move with the door during platform boarding.
Still yet another object of the present invention is to provide a transit vehicle door system for platform boarding or ground level boarding having a threshold which is retained in place when the trap door is in position for platform boarding.
Yet still another object of the present invention is to provide a threshold for a transit vehicle door system having a heater for removal of ice.
In addition to the various objects and advantages of the present invention which have been generally described above, there will be various other objects and advantages of the invention that will become more readily apparent to those persons who are skilled in the relevant art from the following more detailed description of the invention, particularly, when the detailed description is taken in conjunction with the attached drawing figures and with the appended claims.